"MAC" is an acronym for Media Access Control. It's a unique number assigned to every hardware device out there. "Mac" is short for Macintosh.
As far as "writing bad files" goes, that's what happens when you carelessly download and install too much third-party software. Computer novices who believe the Mac is magically pristine in code quality fail to understand that the popularity of Windows makes it popular to budding coders who want to get in on the lucrative industry of software development. Unfortunately, some say it takes genius and OCD to write quality software, and a lot of the applications you find on the Internet really have no business on your computer. But the fact that they're so easy to come by, indeed around every corner as you're surfing the Web, makes it all too tempting. Also, a lot of Windows apps want to autostart with Windows, which Microsoft allows in the name of freedom while Apple discourages it (not necessarily for a bad reason).
As far as cheap parts go, understand that Apple gets all their parts from the same pool of manufacturers PC makers buy from. Don't want a cheap PC? Then don't buy one; nobody is putting a gun to your head. If you can afford $1,000 to buy the cheapest, new MacBook available, then you could be buying a PC whose plastics won't crack like the MacBook's do. And the $2,000 it will take to buy you a MacBook Pro with 4GB of RAM and a 750GB hard drive (not even an SSD for all that money!) could be buying you a powerhouse, HP Envy with 16GB of RAM, 1.5TB of HDD space (or an SSD), and better graphics than any MBP will offer you.
The people who bash Windows the hardest are always the ones who know so little about computers that they can't be trusted with choice, and need a parent to make all their decisions for them. Not everyone is that bad with computers.